%matplotlib inline
from IPython.display import Image
from colour_science import *
Image(electromagnetic_wave_image(), embed=True)
The portion of the electromatic radiation frequencies perceived in the approximate wavelength range 360-780 nanometres (nm) is called the visible spectrum.
visible_spectrum_plot()
Leucippus and Democritus theorised that everything is composed of atoms lying into the void.
Atoms have different size, shape and temperature.
Atoms are moving, indestructible, and invisible.
Solids are made of small pointy atoms and liquids of large, round ones.
Plato held the extramission (emission) theory according to which visual perception is caused by discrete rays of light emitted from the eyes.
Euclid's Optica about the geometry of light, influenced the research of later scientists. He mathematically described the optics law of reflection.
Light reflects from a smooth surface at the same angle that it hit it: the angle of incidence equals the angle of reflection.
He was familiar with the camera obscura principles, observing a partially eclipsed Sun projecting a crescent shape on the ground through the holes in a sieve.
Favoring infinite speed of light, Hero described the principle of the shortest path of light.
A ray of light propagating from point A to point B, in the same medium, has a shortest path length than any nearby path.
Also follower of the emission theory, Ptolemy studied various properties of light: reflection, refraction and colour, establishing the foundations of optics.
Ptolemy's refraction law was inaccurate for large angles and only working for almost normally incident light rays.
Ptolemy described a geocentric cosmology system where the Earth is stationary at the centre of the universe.
In 984, Ibn Sahl was the first to accurately describe the law of refraction.
Alhazen, supporter of the intromission theory, observed that light is emitted by luminous sources as a stream of particles that enters our visual system.
He demonstrated that light travels in straight lines using the camera obscura.
He hypothesized that the speed of light was not infinite although very high and deduced that it was travelling at different speed depending the density of the media being traversed (i.e. refraction).
Opposing to Ptolemaic system, Nicolaus Copernicus formulated the Heliocentrism astronomical model where the Earth is orbiting around the Sun at the center of the Solar System.
In 1621, Willebrord Snellius derived a mathematical equivalent form of the law of refraction.
The ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the reciprocal of the ratio of the indices of refraction.
with each $\theta$ as the angle measured from the normal of the boundary, $v$ as the velocity of light in the respective medium, $\lambda$ as the wavelength of light in the respective medium and $n$ as the refractive index of the respective medium.
In 1637, René Descartes theorised in La Dioptrique on the nature of light.
He used real-world objects (a tennis ball) to define a mathematical model and equation for the law of refraction: the angle of incidence equals the angle of refraction.
In 1637, Pierre de Fermat enunciated the Fermat's principle or principle of least time stating that a ray of light traveling between two points takes the path that can be traversed in the least time.
In 1638, Galileo attempted to measure the speed of light (using the lamps experiment) but was inconclusive, however he supposed that if it was not instantaneous, it must be exceptionally fast.
In 1676, Cassini's assistant danish astronomer Olaf Römer adding to Cassini's own measurement observed that times between Jupiter's moons eclipses got shorter as Earth approached Jupiter, and longer as Earth moved farther away, deducing that speed of light was finite.
Using Römer's data, Christiaan Huygens calculated a speed of light value of 211,000 km/s.
In 1672, he explained the birefringence phenomenon with his wave front theory and evolutes concept.
Published in 1704, Isaac Newton's Opticks investigates the fundamental nature of light and colour using the refraction of light with prisms.
He demonstrated that light is composed of different hues refracted at a peculiar angle by a prism, and that any colour is composed by mixtures of these hues.
He asserted that colour is a visual sensation and not an inherent property of the light or material objects: A magenta (purple) colour can be created by overlapping the red and violet ends of two spectra, but this colour is not found in the visible spectrum.
He showed that two complex lights (composed of more than one monochromatic light) could be perceived as matching even though they are physically different, thus metameres.
Isaac Newton held that the geometric nature of light reflection and refraction could only be explained if light was made of particles (corpuscles), as waves do not tend to travel in straight lines.
Using a telescope, he made supporting observations of the heliocentric astronomical model.
In 1727, James Bradley discovered and measured the aberration of light, a change in the positions of stars caused by the yearly motion of Earth.
This discovery confirmed the orbital motion of the Earth around the Sun and allowed Bradley to estimate the speed of light to be 295,000 km/s.
In the early 19th century, Thomas Young established the wave theory of light pointing at the shortcomings of Newton's corpuscular theory of light.
He demonstrated interference in the context of water waves with the double-slit experiment.
When two Undulations, from different Origins, coincide etiher perfectly or very nearly in Direction, their joint effect is a Combination of the Motions belonging to each. [2]
He proposed the trichromatic colour vision theory, explaining that metamerism is the fact of human visual system conveying colours through a limited number of receptors
In 1818, Augustin-Jean Fresnel building on experimental work by Thomas Young and using Christiaan Huygens’s mathematical principle formally established the wave theory of light.
The Huygens-Fresnel principle states that every point on a wave front become a secondary source of a spherical wave.
He formulated a qualitative explanation of linear and spherical wave propagation, and derived the laws of reflection and refraction using his principle.
However, he could not explain the deviations from rectilinear propagation that occur when light encounters edges, apertures and screens (diffraction).
In 1857, James Clerk Maxwell used linear algebra to prove Young–Helmholtz Theory, invented colour matching experiments and colorimetry.
In 1865, he demonstrated in A Dynamical Theory of the Electromagnetic Field that electric and magnetic fields are transverse waves travelling through space at the speed of light, inferring that light is itself an electromagnetic wave.
Light
Human Visual System
Colorimetry